83Plus:Ports:5A

Synopsis

Port Number: 5Ah

Function: USB Presentation Link Port Mirroring Enable

This port enables or disables the "Presentation Link port mirroring" hardware, which redirects writes to ports 10 and 11 to outgoing bulk endpoint 02. The TI-84 Plus/Silver Edition OS uses this upon connection of the USB Presentation Link adapter.

This port only exists on the the TI-84 Plus and the TI-84 Plus Silver Edition. On the standard TI-83 Plus, it acts as a shadow of port 10. On the TI-83 Plus Silver Edition, this port has no effect.

Read Values

• Bit 0: Set if port mirroring is enabled.
• Bits 1-7: Always 0

Write Values

• Bit 0: Set to enable port mirroring.
• Bits 1-7: Not used

Comments

When this port is set to 1, the USB controller will send a two-byte packet on outgoing bulk endpoint 02 whenever a value is written to ports 10 and 11. You must set up endpoint 02 like this yourself before enabling it.

When enabled, a write to port 10 will cause the following packet to be sent:

<value written to port 10> 00

A write to port 11 will cause the following packet to be sent:

<value written to port 11> 01

This would seem to imply that the second byte is an offset from port 10, but this is untested.

This port only functions in host mode.

Someone with more experience in making guesses as to what the controller and/or hardware is actually doing here should probably provide more input.